The present invention relates to an electromagnetic clutch and more specifically to an electromagnetic clutch which uses the electromagnetic force generated between an electromagnet and a magnetic member and a spring to move the clutch plate carried by a gear into and out of engagement with the magnetic member.
An electromagnetic clutch is disclosed in laid open Japanese Utility Patent Application No. 53(1978)-32191. In this type of electromagnetic clutch, a movable member connected to the input shaft and a movable member connected to the output are opposed to each other. A clutch plate between the members is connected to one of the movable members through a return spring so that the clutch plate is movable in an axial direction. The clutch plate is brought into contact with the other movable member by an attracting force generated in an electromagnet. When the electromagnet is off, the clutch plate is moved away from the other movable member by the power of the return spring so the clutch is disconnected. In practice, a clutch plate or armature plate and a movable member are connected by more than three plate springs placed along the periphery of the rotating axis, as shown in Laid-Open Japanese Utility Patent Application No. 53(1978)-32191. This kind of plate spring looks like a plane plate but the opposite sides and the edges of the plate are slightly different in detail. In other words, each plate has a specific face and back and a desired orientation. Therefore, spring plates may be placed incorrectly when assembled. If a spring plate is misplaced, the gap between the spring and the clutch plate may be too narrow for the clutch to operate accurately. Furthermore, it takes time to place several spring plates in their correct places or it is possible to forget to place some parts when assembling the clutch.